The present invention relates to an apparatus and method for preventing fraudulent uses of a coin operated telephone. More particularly, the present invention relates to an apparatus which comprises conditioning circuitry which incorporates filtering techniques to suppress transients generated within a public coin telephone utilizing an electronic coin validator.
Representative coin validators, currently in use, consist of the AT&T/Lucent Technologies 22 A/B Series Electronic Coin Chute and the LPV 200 WE Series Electronic Coin Chutes manufactured by Mars Electronics International. These units are freely interchangeable with telephone chassis manufactured by a variety of companies.
Under certain conditions (e.g., different combinations of electronic equipment utilized within a standard public coin telephone), fraud can occur, i.e., what is known in the industry as "coin tone" fraud. In this situation, it is possible for users of a public coin telephone to cause the telephone to generate false coin tone signals and thereby make free telephone calls. The end result is that the owner of the public telephone is defrauded.
During normal operation of a public coin telephone, coin tone signals are generated when coins are deposited into the telephone. These tones signal the public switched telephone network as to whether coins have been deposited into the telephone and what the denomination of these coins are.
A public coin telephone contains a coin validator (either fully electronic or electromechanical in nature) and a telephone chassis containing the electronics that control the operation of the telephone and interface the telephone to the public switched telephone network. The coin validator accepts coins deposited by the user and signals the telephone chassis when a valid coin has been deposited. The signaling generated by the validator also indicates to the chassis the type or denomination of coin deposited. The telephone chassis, upon receiving the signals from the validator, generates the corresponding coin tone signals to the telephone network.
Certain combinations of validators and chassis have proven to be subject to compatibility issues which can allow manifestation of the coin tone fraud problem. More specifically, the fraud is created by the user flashing (quickly depressing and releasing) the hook switch on the telephone. This operation causes a brief interruption of the power to the chassis and validator. Under this condition, certain combinations of validators and chassis may cause the erroneous generation of coin tone signals, thereby indicating false coin deposits into the telephone. Typically, the coin tone signals being generated to the telephone network can be faintly heard in the telephone handset receiver. A user, once aware of this condition, could freely cause the telephone to signal false coin deposits and thereby allow the user to make free telephone calls as noted above.
An object of the present invention is to eliminate this problem in a simple, inexpensive and effective manner by providing an external plug-in module, which inserts between the validator and the chassis and has circuitry to "condition" the coin signals generated by the validator. This signal conditioning eliminates the possibility of the chassis being improperly triggered, thereby eliminating the possibility of generating false coin tone signals during periods of interrupted power.
The circuitry according to the present invention incorporates standard filtering techniques to suppress any transients that might be generated during interruption of power to the chassis and validator. These transient may also take the form of voltage spikes in the order of micro-seconds or less.
The filter of the present invention does not drastically alter the nature or timing of the signals generated by the validator and can be used with any combination of validators and chassis that might be encountered in application. Due to the plug-in nature of the module, it has the substantial advantage of being field retrofittable into the public coin telephone and does not require modification to any of the telephone's components, including the validator and chassis.
The module itself, in accordance with the present invention, is comprised of a small housing that can be made of a variety of materials including, but not limited to, plastic or metal. One end of the housing contains a 15- pin subminiature D male connector. The other end of the housing contains a 15- pin subminiature D female connector. These connectors, in turn, mate with the corresponding conventional connectors located on the validator and chassis. No other connections are required for the module to function.
Another object of the present invention to provide an external plug-in module that will eliminate potential coin tone fraud.
It is a further object of the invention to provide an external plug-in module that will work with any combination of validator and telephone chassis.
It is still another object of the present invention to provide an external plug-in module that is completely self-contained.
It is a further object of the present invention to provide an external plug-in module that can be field retrofitted.
Another object of the present invention is to provide an external plug-in module that is transparent to normal signaling.